<!DOCTYPE html>
<html lang="zh">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

</body>
<script>
  const obj={};
  /*js中对象的key只能是String类型，使用对象作为key时，会自动调用对象的toString()方法，结果为[object Object]*/
  const obj2 = {
    name:"张三",
    [obj]:"对象"
  }
  alert(obj)
  console.log(obj)
  console.log(obj2)

  const obj3 = {name:"张三",age:18}
  const obj4 = {name:"李四",sex:"男"}

  const obj5={...obj3,...obj4};
  console.log(obj5);

  const obj6={...obj4,...obj3};
  console.log(obj6);

  function f1(x,y) {
    /*x的值为null,undefined,false,"",0时，赋值1，否则赋值原值*/
    // x = x || 1;
    // y = y || 2;
    /*x的值为null和undefined时，赋值1，否则赋原值*/
    x = x ?? 1;
    y = y ?? 2;
    console.log(x+y)
  }
  f1(0,0)

  function success(res) {
    if(res&&res.code === 200){
      console.log(res&&res.data&&res.data.filename)
    }else{
      console.log("参数异常")
    }
  }
  success({code:200,data:{filename:"abc.png"}});
  success();

  function success2(res) {
    if(res?.code===200){
      console.log(res?.data?.filename)
    }else{
      console.log("参数异常")
    }
  }
  success2({code:200,data:{filename:"abc.png"}});
  success2();
</script>
</html>
